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Low-humidity sensors were made by layer-by-layer (LBL) self-assembly of poly(4-styrenesulfonic acid-co-maleic acid) (PSSMA) or poly(styrenesulfonic acid) sodium salt (PSS) and poly(allylamine hydrochloride) (PAH) into multilayer thin films on a gold electrode of quartz crystal microbalance (QCM). The thin films were characterized by QCM and atomic force microscopy (AFM). The effects of maleic acid (MA) in PSSMA, the number of layers and the ionic strength on the low-humidity sensing properties (sensitivity) were compared with those of PSS. The sensitivity of the PSSMA/PAH multilayer thin film exceeded that of the PSS/PAH multilayer thin film when the multilayered thin films of polyelectrolytes were prepared from solutions without NaCl. The sensitivity of both PSSMA/PAH and PSS/PAH multilayered thin films was increased by increasing the number of layers and by adding salt to the deposition solution. The PSS/PAH multilayered thin film that was prepared from the solutions with NaCl had the highest sensitivity (1.923 −ΔHz/Δppmv at 27.5 ppmv) and a short response time. Spin-coating was also adopted to fabricate PSS-based low-humidity sensors for comparison. 相似文献
3.
Suspended sediment and organic contaminants were measured during a period of 2 years in the San Lorenzo River, central California, which discharges into the Pacific Ocean within the Monterey Bay National Marine Sanctuary, in an effort to quantify the potential environmental effects of storm events from a steep, mountainous coastal urban watershed. Most suspended sediment transport occurred during flooding caused by winter storms; 56% of the total sediment load for the 2‐year study was transported by the river during one storm event in January 2010. Concentrations of polycyclic aromatic hydrocarbons can exceed regulatory criteria during high‐flow events in the San Lorenzo River, and total annual polycyclic aromatic hydrocarbon load was on the order of 10 kg in water year 2010. These results highlight the importance of episodic sediment and contaminant transport in steep, mountainous coastal watersheds and emphasize the importance of understanding physical processes and quantifying chemical constituents in discharge from coastal watersheds on event‐scale terms. Published 2012. This article is a U.S. Government work and is in the public domain in the USA. 相似文献
4.
Marcia C. Delpech Ivana L. Mello Fernanda C. S. Delgado Jurandir M. Sousa 《应用聚合物科学杂志》2012,125(5):4074-4081
The extender oil usually employed in compositions of rubbers based on styrene and butadiene (SBR) 1712 is the distilled aromatic extract (DAE). In this work, this oil was substituted by oils with low levels of polycyclic aromatic hydrocarbons (PAHs): treated residual aromatic extract (TRAE) and two naphthenic oils from different suppliers (HN1 and HN2). This substitution was performed in response to REACH Regulation (EC No. 1907/2006 European Parliament and the Council of December 18, 2006, Annex XVII), which state that the sum of individual PAHs should be below 10 mg/kg and the levels of benzo (a) pyrene (BaP) should not exceed 1 mg/kg. Infrared spectroscopy was employed to characterize the structure of crude oils and respective SBR compositions. Thermal properties of the materials were evaluated by thermogravimetry and differential scanning calorimetry. Mechanical properties as tension tests, hardness, abrasion resistance, and resilience were also determined. The final results showed that it is possible to replace the extender oil DAE for any of the oils tested, specially the naphthenic HN1, without any loss of the properties evaluated in this study for the SBR compositions. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012 相似文献
5.
A.R. Lea-Langton D.V. Spracklen S.R. Arnold L.A. Conibear J. Chan E.J.S. Mitchell J.M. Jones A. Williams 《能源学会志》2019,92(3):587-593
Combustion of wood and other biomass is a significant contributor to poor air quality in many developing countries. Emissions of particulates and Polycyclic Aromatic Hydrocarbons (PAH) are a major health hazard, particularly in Africa where the use of domestic cookstoves has increased alongside population expansion. Because of economic factors firewood is commonly used in place of the more expensive charcoal; particularly in rural areas. This work conducts a study of PAH emissions from an African cookstove comparing the combustion of both charcoal and firewood. It is demonstrated that PAH and particulate emissions are much higher from the firewood compared to the charcoal. The difference in levels can be interpreted due to the importance of the pyrolysis reactions of the volatile components of wood in PAH formation, whereas these volatiles emissions are much smaller from charcoal. Analysis of the combustion phases (flaming, smouldering) is undertaken and a computer model has been developed to link the composition of the fuels to the emissions of the PAH and particulates. The modelled PAH levels are shown to follow a similar trend to the experimental results. 相似文献
6.
Maiqian Nie Hongyun Nie Wen Cao Xiaodou Wang Yutao Guo Xiaoting Tian 《Polycyclic Aromatic Compounds》2016,36(2):132-151
A new polycyclic aromatic hydrocarbon (PAH)-degrading Gram-negative bacterium Aeromonas salmonicida subsp. achromogenes strain NY4 was isolated from coking wastewater sludge. Strain NY4 could not grow on1-hydroxy-2-naphthoic acid, hexadecane or hexanol as sole carbon source but phenanthrene. This strain was able to utilize several known microbial metabolites of PAHs, including catechol, protocatechuic acid, salicylic acid, and phenol as sole carbon source. The mixture of the acidic and neutral fraction, acidic fraction alone and neutral fraction alone of phenanthrene metabolites were prepared and analyzed by GC-MS. A total of at least 27 metabolites were identified as the degradation products of phenanthrene by strain NY4. Among them, 1-hydroxy-α-oxo-2-naphthaleneacetic acid, 2-hydroxy-α-oxo-1-naphthaleneacetic acid, 2-hydroxy-1-(1-hydroxy-2-naphthalenyl)-ethanone, 1,2-dihydro naphtha [2,1-b] furan-2-ol and 2,3-dihydro naphtha [1,2-b] furan-2-ol have not been reported as the metabolites of phenanthrenes so far. The accumulation patterns of phenanthrene metabolite accumulation by strain NY4 depended on the incubation time, inoculum size and concentration of phenanthrene. Based on the degradation metabolites of phenanthrene by strain NY4, degradation pathways are proposed. This is the first report of PAH degradation in Aeromonas salmonicida, which lay the foundation for recognition and further characterization of PAH degradation metabolites and pathways in Aeromonas salmonicida strains. 相似文献
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The polycyclic aromatic hydrocarbons (PAH) in Egyptian condensates are analyzed for the first. A solid phase extraction (SPE) followed by gas chromatography-mass selective detection was used for their analysis. The method was calibrated for optimal extraction conditions. Excellent recoveries were found (78–114%) for the PAHs that were identified using a variety of standards and GC-MS spectra. The solid-phase extracted PAH fraction was further separated by HPLC on a Ag(I) mercaptopropanosilica gel to reduce the complexity of the sample by separating the PAHs based on the number of aromatic rings. The analytes were quantified using GC with a flame ionization detector. For this kind of sample SPE is a more convenient separation technique than an open column. PAHs containing two to four rings in the concentration range 0.6–11 μg/L were measured. Some preliminary geochemical hypotheses based on the analyzed PAHs and the previously analyzed S-containing aromatic compounds were formed as to the depositional environment and source rock type. 相似文献
9.
Omowunmi H. Fred-Ahmadu 《Polycyclic Aromatic Compounds》2013,33(4):383-393
ABSTRACTThis study describes a survey of polycyclic aromatic hydrocarbon (PAH) concentrations in 23 green, herbal, and black tea brands widely consumed in Nigeria by determining the levels of benzo[a]pyrene, chrysene (PAH2), benzo[a]pyrene, chrysene, benz[a]anthracene, benzo[b]fluoranthene (PAH4), benzo[a]pyrene, benz[a]anthracene, benzo[k]fluoranthene, chrysene, benzo[b]fluoranthene, dibenz[ah]anthracene, benzo[ghi]per-ylene and indeno[1,2,3-cd]pyrene (PA-H8). Toxic equivalence factor and mutagenic equivalence factor were applied to evaluate the toxic equivalence and mutagenic equivalence quotients relative to benzo[a]pyrene. The concentrations of PAHs indicate that Regulation 835/2011/EC was not fulfilled by benzo[a]anthracene, B[a]A, benzo[a]pyrene, B[a]P, benzo[b]fluoranthene, B[b]F, and chrysene, CHR. The PAH4 levels ranged from 1.28 to 44.57, 4.34 to 11.20, and 0.76 to 34.82 µg/kg in green, black, and herbal tea products, respectively. On the other hand, the PAH8 concentration varied between 1.63 and 65.73, 5.02 and 68.83, and 12.43 and 24.92 µg/kg in green, herbal, and black tea samples. The PAH4 and PAH8 provide more reliable indicators for determination of PAH contamination and risk characterization in food than PAH2. 相似文献
10.
M.S. Callén M.T. de la Cruz S. Marinov R. Murillo M. Stefanova A.M. Mastral 《Fuel Processing Technology》2007
The electron beam technology (EBT), proven treatment for SO2 and NOx removal, is applied to different power stations as hot gas cleaning system. In this paper, an assessment of this technique installed in a Bulgarian power station on organic emissions is analyzed. The Polycyclic Aromatic Hydrocarbons (PAH) content, not only emitted in the gas phase but also trapped in the solid phase, has been carried out before and after the irradiation. The main aim has been to know whether the EBT affects organic emissions, like PAH, as it happens with inorganic pollutants, like SO2 and NOx, studying EBT effects from an organic environmental point of view. 相似文献